Traffic signal



Sept. 20, 1938. R. c. HITCHCOCK 2,131,009

TRAFFIC SIGNAL Filed May 6, 1951 3 Sheets-Sheet 1 WITNESSES: INVENTOR WJW mammary/1617mm Sept. 20, 1938. R. c. ILIITCHCOCK TRAFFIC S IGNAL Filed May 6, 1951 3 Sheets-Sheet I5 39/ INVENTOR WITNESSES:

Patented Sept. 20, 1938 UNITED STATES PATENT OFFIQE TRAFFIC SIGNAL Application May 6, 1931, Serial No. 535,366

3 Claims.

My invention relates to traflic-control systems and has particular relation to traffic-control systerms of the type wherein the timingof signals controlling the flow of traffic along a plurality of 5, highways is regulated by the density of the traflic along such highways.

It is an object of my invention to provide a traffic-control system for an intersection of a plurality of highways wherein the signals shall be regulated in accordance with the density of the trafiic along such highways.

Another object of my invention is to provide a traffic-control system for a plurality of intersecting highways wherein the period of time during which a go signal is displayed along a highway shall be directly dependent upon the density of the traffic along that highway.

It is a further object of my invention to provide a traffic-control system for a plurality of 20 highways of a type incorporating a plurality of stop and go signals to be displayed along each of the highways in a predetermined cyclical sequence, the relative duration of the stop and go signals for each highway during each cycle being dependent upon the density of the traffic along that highway.

A still further object of my invention is to provide a trafiic-control system for a plurality of highways which shall incorporate a plurality of 3;) stop and go signals to be displayed along each of the highways, the duration of the display of the go signal along the highways being dependent upon the total number of vehicles awaiting the display of the signal.

Still another object of my invention is to provide a traffic-control system of the type that shall incorporate a plurality of stop and g signals to be displayed along a plurality of highways and a plurality of street devices, the character of the display of the stop and go signals being dependent upon the period of time during which a street device is actuated.

An incidental object of my invention is to provide for a traflic-control system of the type incorso incorporating a normally energized photo-sensiporating a plurality of stop and go signals to.

tive trafiic-density-regulating system, a device that shall render the traffic-density-regulating system inoperative when the photo-sensitive device associated with the system has been deenergized for an inordinately long 'period of time.

More concisely stated, it is an object of my invention to provide a simple and efiicient trafiicdensity-regulating device for a trafiic-control system of the type incorporating a plurality of stop and go signals to be displayed along a p1u rality of highways through which the trafiic is of substantially equal average density.

According to my invention, I provide a trafiiccontrol system of the type incorporating a plurality of stop and go signals to be sequentially displayed along a plurality of highways.

In a preferred embodiment of my invention, a go signal is displayed along one of the highways, while stop signals are displayed along the other highways. I The signals are periodically varied in such manner that the go signal is given to all of the highways in turn.

The sequential operation of the signals depends upon a program controller, the segments of which are connected in series with power sources and with the signals. The program controller is driven by an induction motor which is normally energized from an alternating-current-supply source, but is capable of being energized for a short period of time from a direct-current source in response to the actuation, by a vehicle, of one of a plurality of street devices disposed along the highways. The street devices are, preferably, of the photo-sensitive type, and, when the radiations that normally energize the photo-sensitive element incorporate-d. therein are obstructed, the direct-current-power source is instantaneously applied to the motor to effect a decrease in its speed of rotation.

The street devices are so associated with the relays, whereby the motor is energized from the direct-current source and with an appropriate rotating sector, that actuation of the street device by a vehicle is only effective in applying the direct current to the motor when the vehicle is moving along the highway for which a go signal is being displayed. If the vehicle is moving along a highway for which the stop signal is displayed, it has no effect on the relays whereby the motor is energized through the direct-current-power source.

It is apparent, therefore, that the period during which a go signal is displayed for one of a plurality of highways that are regulated by a traffic-control system, constructed according to my invention, is dependent upon the densities of the traffic along such highways.

It may happen that, along a certain highway, the source whereby the photo-sensitive device is energized may be extinguished, or again, a vehicle may be stalled directly in the path of the source. sensitive device will be deenergized foran inordinately long period of time, and the motor will be operated during this period of time partly from the alternating-current-supply source and partly;

from the direct-current-supply source.

By reason of the fact that such situation'is' undesirable, I have provided .a.-thermostatic relay-.-

that is so connected in the trafiifcsignal-control circuit that, if the photo-sensitivedevice--is1 deenergized for an inordinately long period of time, the circuit, whereby the direct-current power issupplied to the motor, is opened and thee-system:

continues to operate in the ordinary programcontrol time periods until the photo sen-sitive device is again energized.

In a preferred modification of my invention, the traflic signals are displayed insequence and are varied continually; I have provided-also a system wherein a caution signal is normally displayed along a plurality of highways. A plurality of street devices are disposed along the highways and, when one of thedevices is actuated, a go signal is displayed for the particular highway along which the actuated street device is disposed. In such case, the traflic-signalling system passes through a cycle, and a go signal for the highway and a stop signal for the remaining highways are displayed for a predetermined period of time, determined by the number of vehicles that actuate the-street deviceafter the operation of the signalling system has been initiated.

The program controller, in apparatus of this type, is driven by an induction motor, to the terminals of which either'direct current or alternating current may be applied. Normally, the caution signal is displayed along the highways, and direct current'is appliedto theinduction motor. When a street device'along a certain highway is actuated, the direct-currentpower source is disconnected from the terminals of the motor and alternating-current power is supplied. The motor is then rotated until a caution signal is again displayed along" the highways. During the rotation of the motor, the direct current may be intermittently applied to its terminals by theco-action of the street device and a vehicle moving along the-highway for which the go signal is displayed.

According to a further modification of my, invention, the duration of the go signal displayed for a highway. is dependent upon the number of vehiclesthat were waiting for the signal to be displayed.

In this system, the programcontroller', whereby the sequence of the signals is regulated, is driven by a direct-current motor. The street devices are operatively associated with ratchet relays, whereby the resistance connected in the windings of the motor may be varied in accordance with the number of times the ratchets associated with the relays are actuated. The ratchets are actuated once, for each interruption of the current, through tl'ie'photo-sensitive devices. Consequently, the resistance connected in series with the windings of the'motor increases as the. number of times that'the'street devices are actuated increases. In this modification of In such case, the corresponding photoseries with the windings of the motor.

my invention, only the ratchet associated with the highway for which a stop signal is displayed is actuated during any given cycle.

The street devices disposed along the highways are spaced from the point at which the traffic signals are disposed and, as the vehicles actuate the particular street device associated with the highway for which the go signal is being displayed, the ratchet relay adds up the. number of resistor elements that are to be included in When the go signal is displayed for the highway in question,: the motor rotates at a speed predetermined by the. number of vehicles that have actuated the vstreet;device.

By reasonofthe-fact that the street devices are spaced from the signals, certain vehicles may actuate the street device while the go signal. is'still being displayed for the highway along which they are moving and may arrive in the-vicinity of-the signal after the top signal has'been displayed. The count of the ratchet relay will not be accurate, therefore, unless the counting starts a short time before the period of 'display of the go signal for the highway.

has terminated. In practice, the alternate counting of the resistor elements. may be so timed that substantially all the carswaiting .'for

a-go="signal along the highway at a predetermined instant are counted.

By reason of the fact that, inmy improved traifi'c-control system, the street devices are. ordinarily of the photo-sensitive type, the photosensitive element may be deenergized continuously for a comparatively long period OfTlJiIile: by a succession of cars moving in staggered relation ship along a highway. I have; therefore, pro videda circuit'interrupterwhereby the counting continues'when suchsituation is encountered;

The artificial counting maybe adjusted in any desired' manner-to conform totlie-velocity of the vehicles as they normally: move along the"high way.

The novel features thatI consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, howevenboth' as toits organization and its method of operation, together witl'ra'dditional objects and advantagesthereof, will b'est'abeunderstood from the following description of specific embodiments, when read inaconnection withthe accompanying drawings in which:

Figure 1 is a diagrammatic view showing the circuits of a preferred'embodim'ent of'myinvention,

Fig. 2 is a diagrammatic'view showing a modification of'my inventionwhereir'i it' is'applied to a traffic-control system of the vehicle-actuated type.

Fig. 3'is a diagrammatic view showinga'modi fi'cation of a type wherein the timing of the signals along a highway isregulated in accordance with the vehicle trafiic awaiting thego'signal for that highway.

The apparatus shown in Fig; 1' comprises a plurality of stop"' signals 8 and 2', caution signals 3 and i and go signals and fi disposed at the intersection i 'of'a plurality of highways 9"and ii. The signals 2, 3, i; E'and ii are capable of being energized through the segments 53, i5, ii and IQ of a programcontroller 21in such manner that the stop, caution and highways 9 and ii.

The circuit througl1'the-'-stop signals- I along the highway 9 and the go signals 6 along the other highway II extends from one alternatingcurrent power-supply bus 23, through conductors 25 and 21, a'brush 29 in engagement with a collar 3| secured to the shaft 33 of the programcontrol motor 35 and rotated thereby, a movable contactor 31 rotated by the shaft 33, the conducting segment I3 in engagement with the contactor 31, conductor 4|, the stop signals I and the go signals 6, connected in parallel and con ductor 43, to the remaining bus line 45 of the alternating-current source.

The remaining sets of stop and go signals are energized through the other segment I 5 of the program controller 2| which is capable of being engaged by the contactor 31, while the caution signals 3 and 4 are energized through the sectors I1 and I9 that are rotated by the shaft 33 of the program-control motor 35 to engage a brush 41 during a predetermined period of its rotation.

The motor 35, whereby the program-control contactor 3'! and segments I1 and I9, are rotated, is of the alternating-current induction type and is energized from the alternating-current-power source through a capacitor 49 of suitable character, the purpose of which will be explained hereinafter. I

The time of display of the signals along the highways is controlled from a plurality of street devices disposed along the highways. Although the street devices may be of any of the types well known in the art, such as the mechanical-contactcr type or. the acoustic type, I have found that the photo-sensitive type is preferable. The preferred street devices, therefore, comprise a plurality of sources 5! and 53 of radiant energy disposed on one side of each of the highways 9 and a plurality of photo-sensitive devices 55 and 51 disposed on the other side of each of the highways in such positions as to be influenced by the radiation from the sources.

When the radiations from the light source 53 to the photo-sensitive device 51 are interrupted by vehicles moving along the highway II for which the go signals 6 are being displayed, the exciting coil 59 of relay 6|, associated with the photo-sensitive device 51, is deenergized, and a circuit is completed from a direct-current bus line 63, through conductor 65, a movable contactor 5? of the relay Ii! that has engaged its corresponding fixed contactors 69 by reason of the deenergized condition of the relay coil 59, conductor ii, a conducting segment 13, symmetrically disposed relative to the shaft 33 of the program control motor 35, a movable contactor 15, in engagement with the conducting segment H and rotated from the shaft 33, a collar 11 secured to the shaft 33, a brush 19 in engagement with the collar 11, conductor 8|, the movable contactor 83 of a relay 85, conductor '81, the exciting coil 8:) of another relay 9!, conductors 93 and 95, a movable contact 91 of a thermostat relay 99, the fixed contactor I9I of the relay 99 and conductors I93 and I95, to the remaining directcurrent terminal I 01.

The relay 9I, through the coil 89 of which the current is now flowing, is energized to close a circuit from one direct-current bus line 63, through a suitable resistor I09, a movable contact-or III, associated with the relay 9I that is new in engagement with its corresponding fixed contactors M3 by reason of the excitation of the relay 9i, conductors H5 and H1, the windings of the program-control motor 35, conductors H9 and I2I, a second movable contactor I23 of the relay SI and conductor I25, to the remaining direct-current terminal I01.

Direct current is thus applied to the windings of the motor 35, and the speed of the motor is, consequently, decreased. The direct current through the windings of a motor is blocked from being shunted through the alternating-current source by the capacitor 99 connected in the power-supply line of the motor.

It is apparent that the length of the period during which the motor 35 is reduced in speed and also the number of times that the motor is reduced in speed depends upon the density of the trafiic along the highway for which the g signal is being displayed. It is to be noted that the movable contactor 31, whereby the go signal or 8 is energized for a particular highway 9 or II, is oriented on the shaft 33 of the motor 35 in the same angular position as the contactor 15, whereby the activity of the speed-reducing device is controlled. The corresponding fixed contacts 53 and I5 and 13 and I21, which are respectively engaged by the movable contactors 31 and 15, are also similarly oriented relative to each other and, consequently, the speed of the motor is controlled only from the highway for which the go signal is being displayed and not from the highway for which the stop signal is being displayed. In the example herein set forth, the speed-control device for the motor is operated from the highway II The circuit for controlling the speed of the motor 35 from the other highway 9 is closed through the contactor H29 of a relay I3I that is deenergized when the photo-sensitive device 55, associated with the highway 9, is deenergized and extends from one direct-current power line 63, through conductor 55, conductors I33 and I35, the movable contactor I29 of the relay I3I, associated with the street device 55, conductor I31, the segment I21, oriented in a position corresponding to the orientation of the segment I5, whereby the go signal 5 is displayed for the highway 9, the movable contactor 15 when it is engaged with the segment I21, the collar 11, the brush 19 in engagement with the collar 11, conductor til, the movable contactor 83, conductor 81, the exciting coil 89 of the relay BI, whereby the direct-current power is supplied to the motor 35, conductors 93 and 95, the movable contact 91 of the thermostat 99, the fixed contact IBI, of the thermostat 99 and conductors I93 and 555, to the remaining direct-current bus line I91.

If it so happens that one of the photo-sensitive devices 55 and 51 is deenergized for an inordinately long period of time, as, for example, by a vehicle that stalls in the path of light or by the extinction of one of the light sources 5I and 53, a heating element I 39 is energized. The heating element is connected in a circuit that extends irom one direct-current bus line 53, through conductor 65, the conductor I 33 for the photo-sensitive device 55 or the conductor I40 for the photo-sensitive device 51, the movable contactor MI, associated with the relay I36, or the movable contactor I43, associated with the relay IiI, conductor I35 or conductor I 41, the common conductor I49, the heating coil I39 of the thermostat 99 and the conductor I05, to the direct-current bus line I01.

When the thermostat coil I39 attains a temperature predetermined by the length of the period of time during which the photosensitive devices 55 or 5? remain deenergized, the movable contact 91 of the thermostat 99 is disengaged from its fixed contact. IOI and the circuit through the coil 89 of the relay 91; w-hereby direct current issupplied to the motor 35, is opened.

The circuit whereby. the direct current is supplied to the motor 35 is, moreover, held permanent-ly open by reason of the'fact that a circuit through the exciting coil II of the relay 85, through the contactor 83 of which the relay 9| is energized, is opened, The circuit through the exciting coil 89 of the relay 9I now remains open in spite of the fact that the heating coil i319 may decrease in temperature to such an extent that its contacts 9-! and Iill become engaged as long as thephoto-sensitive devices 55- and 52- remain deenergized,

However, if thephoto-sensitive devices 55 and 51 are both reenergized, the heating coil 539 is disconnected from the circuit, and the lower contactors I53 and 3520f the relays I3I and 55, as sociated with the photo-sensitive-street devices 55 and 51, are againengaged with their fixed contacts I5? and I59: If the coil I59 of the thermostat 99. is now sufficiently cooled, a cir cult is closed which extends from one directcurrent bus 1ine53, through conductor Mil, the

exciting coil I5;I- of the relay 85, conductor 163, the movable contactor' I55, conductor i551, the movable contactor-l 5.3 of the relay I3 I-, conductors I91 and 95, thecontacts 91 and IIJI of the thermostat 99, and conductors I93 and N35, to the direct-current bus line I01.

The function of the relay 85, as is apparent from the above description, is to prevent the direct-current: circuit through the motor 35 from being reclosedwhen thethermostat coil R39 is again coo1ed, after ithas-once been open, by reason of a defective condition in the system. Bythearrangement set forth above, the direct current can only be-suppliedto the motor 35 if both of the-devices55and 51 are energized.

In Fig. 2, a system is shown wherein the opera tion of the signals-1,2, 3, 4,5and- 6 is initiated by thecoaction ofa vehicleand-a street device which is, in thepresent case,,a photo-sensitive trigger. The system isparticularly adapted to be utilizedat the intersectionl59 of a mai or highway I'I I- and a minor lane I13, as shall be explained hereinafter.

Under normal circumstances, the caution signals3-and i-areconnected in a circuit extending from one alternating-current bus line 23, through-conductors I and Ill, a brush H9 in engagement with a collar I8 I, rotated on the shaft 33; of an inductor motor 35, whereby the program controller I83,0i the'system is rotated, the collar l8i,,a bus line I9], connecting the collar WI and a segment I89 on'aninsulating disc i9! rotated by the motor 35, the segment 589, a brush I93. in engagement with the segment I89, conductor I95, the caution signals 3 and 5 and conductor I97 to the; remaining alternating-current bus line 45.

Aplurality of photoesensitive devices 599, ZilI, 293 and 295 are disposed along the highway Ill andthe lane I'i3, and a. plurality of sources 297, 259', 2H: and 2I3 are disposed opposite to the photo-sensitive devices in such manner that the light from the sources is to beinterrupted by a vehicleapproaching the intersection along the highway or a lane.

The motor 35, whereby the program controller I9I isactuated, is of the-alternating-current inductiontype normally connectedin a direct-current circuit that extends from one direct-currentbus lineiit", throughconductors 2-I5 and 2H,

the windings ofthe motor. 35, conductors-2H and 22 I the movable contactor 2-23, of arelay 225 that is in engagement with. its corresponding fixed contacts 221, and conductors 229 and 23I- to the remaining direct-current bus line, N11,.

The relay 225, whereby direct current is supplied to the'motor 3,5; isheld in. energized condition. by reason of, the. fact that. its coil. is connected in a circuitextending. from one directcurrent bus line 63 through conductor 233, the movable contactor 2.35. of a. relay 231 associated with the photo-sensitive triggers. provided for the lane I73, conductor. 239, the, movable, contactor 245 of: a relay. 243 thatis associated with the photo-sensitive triggers providedrfor the highway Ill, conductor 245, a conducting segment 24'! disposed adjacentto'theshaft 3,3 of; theprogramcontrol motor-35., a movable contactor 249 rotated by the program control= motor, a collar 25I rotated by the motor, a.brush-. 2.5.3 in engagement with the collar 25 I, conductor. 255, the excitingcoil 257, of the relay 225, andconductors229 and 23I to the remaining. directrcurrent. bus line I91.

If one of the beams, oflighttransmitted across the highway. I'llv isinterrupted, one of the photosensitive devices.l99;and,293, associated with the highway, is deenergized, and the relayv 2 33., associated-with. the photorsensitive devices I 99 and 253, is also deenergized. 'Ilhecircuit throughthe exciting 0011.251. of the relay 225, whereby direct currentis suppliedto, the motor 35, is broken, and. the-circuit,. whereby direct, current. is supplied tothe motor, is. opened, while the second circuit, whereby. alternating current is supplied to the motor, is closed.

The latter circuit. extends from one alternating-current bus line.;23, through acapacitor 259, the windings of themotor 3t5, conductor 299, a movable contactor ZSI that engages. a, plurality of fixed contacts263 when the relay 225, whereby direct current is suppliedto the motor,.is deenergized. and conductorf265, to theremaining alter" nating-currentbus line 452 a The motor 35. is now effectively energized and rotates in, a clockwise direction. In rotating, it disengages the moyable contactor 259, whereby the relay 2-25,,through which the direct current was supplied to themotor, was-energized, from its corresponding segment 241'; The circuitthen remainsbroken untilthe movable contactor 249 returnsto the fixed segment 247. On, the other hand/the segment. I89; whereby the caution signals 3, and 4 were energized, is disengaged from the brush. i93andthe stopsignal 2; and the go signal 5 is,,at ,the. same. time, connected in a circuit extending from. one alternating-current bus line. 23, throughconductors H5 and 25?, a brush 259 inengagementwitha collar 2H secured to the shaft 33ofthe motor 35, a.mo vable contactor 253 rotated by.t-he-motor.35., asegment2l5 symmetrically disposed relative tothe shaft 33 of the motor 35 with which themovable contact is now engaged, conductor. 2H, theisignals 2 and. 5 and conductor Hi, to the. remaining, alternating current bus line 45.

A go signal is nowv displayed for. the major highway ill, and a.stop. signal is displayed for the minor highway. I13.

Moreover, if a second vehicle should now interrupt the beam of light associated-with the major highway HI while the go. signal 5 is being displayedfor the highway, acircuit is closed from one direct-current bus-,line- 53, through conductors 2'49, 28Lan'd 283, the lower movable contactor 255 of the relay, 243., associated. with the ph0to-sensitive trigger, provided for the major highway l1l, that is now in engagement with its fixed contacts 231 by reason of the fact that the relay 243 is deenergized, conductor 289, a fixed segment 29| symmetrically disposed relative to the shaft 33 of the motor 35, a movable contactor 293 now in engagement with the fixed segment 25! a collar 235 secured to the shaft 33 of the motor 35, a brush 231' in engagement with the collar 295, conductor 299, the exciting coil of a relay 383 and conductor 335 to the remaining direct-current bus line H81.

By reason of the fact that the relay 333 is now energized, direct current is supplied to the motor through a circuit extending from one directcurrent bus line 63, through conductors H5 and 2, the windings of the motor conductors 2| 9 and 301, a variable resistor of appropriate magnitude, conductor 3! I, the movable contactor 3! 3 of the newly energized relay 353 that is now in engagement with its corresponding fixed contacts 315 and conductor 23I to the remaining direct-current bus line I81. Since the motor 35 is now partly energized by direct current and partly by alternating current, its speed is decreased, and the period of time of the display of the go signal 5 and the stop signal 2 is increased.

On the other hand, if a vehicle advancing along the minor highway 413 interrupts an exciting beam of light transmitted across that highway, while the normal caution signals 3 and 4 are being displayed at the intersection I59, the relay 23'! is deenergized, the circuit through the exciting coil 251 is opened by the disengagement of the movable contactor 235 from its corresponding fixed contacts and the motor 35 whereby the program controller is rotated becomes energized from the alternating-current-power-supply source and remains energized by the subsequent disengagement of the movable contacts 249 from the fixed contact 241. As the program controller I83 is rotated, the movable contactor 213 en-' gages successively its corresponding fixed contacts. Accordingly a stop signal 2 is first displayed for the highway I13 and a go signal 5 for the highway l1! and then a go signal 5 is displayed for the highway 413 and a stop signal I5 is displayed for the highway Hi.

It is felt that, while a system such as has been described hereinabove may be disadvantageous for certain intersections by reason of the fact that the traffic along each of the highways passing through the intersections is substantially equal, to that along the other, it is particularly useful for intersections wherein the traffic along themajor highway ill is heavy, as compared with the trafiic along the minor highways I 33. It

is highly desirable that an intersection of a highway and a lane be cleared of vehicles before the go signal for the lane is displayed and, since the trafiic along the major highway is comparativelyheavy, a considerable period of time is required for the intersection to be cleared. The

3 period of time is occupied by the display of the stop signal for the lane.

It should be noted that, regardless of what system is utilized, the time of display of the go signal 6 for the lane 13 may be prolonged by the movement of additional vehicles along the lane after the first vehicle has passed. When the go signal is displayed for the lane N3, the relay 353, whereby direct current is applied to the motor, is energized by the coaction of the street device and vehicles moving along the lane I13, through the contactor 3i 1 of the relay 231 and through the segment 3|9 that is in engagement with the movable contactor 293 when the go signal is displayed.

The apparatus shown in Fig. 3 comprises a signalling system disposed at the intersection 1 of a plurality of highways 9 and H along which the traifio is normally, substantially of equal density and comprising a plurality of stop signals l and 2, caution signals 3 and 4 and go signals 5 and 6.

Street devices, comprising sources of light 32! and. 323 for projecting a beam across the highways 9 and H, and photo-sensitive devices 325 and 321 on which the beams impinge, are disposed along each highway at a predetermined distance from the intersection 1.

The program controller 329, whereby the sequential display of the signals along the highway is controlled, is rotated by a direct-current motor 33!, the winding 333 of which is to be connected in series with a plurality of resistor elements 335 and 331. The resistor elements are engaged by movable contactors 339 and 3M that are actuated by the one or the other of a plurality of latch relays 343 and 345, the coils 341 and 349 of which are, in turn, excited from the one or the other of the photo-sensitive triggers.

Under normal circumstances, the stop, caution and go signals I, 2, 3, 4, 5 and 6 are displayed in sequence for the highways 9 and l i.

As shown in Fig. 3,.the motor 33! is energized through the resistor 331. The stop signals i and the go signals 6 are energized through the segment 356 of the program controller 329. As the elements of the program controller are rotated, the brush 352 disengages the segment 358 to deenergize the stop signals I and the go signals 6 and the brush 354 engages the segment 355 to energize the caution signals 3 and 3. As the elements are further rotated, the brush 354 is disengaged from its corresponding segment 355 and the caution signals 3 and 4 are deenergized and the brush 352 is engaged with another segment 358 to energize the stop signals 2 and the go signals 5. If a vehicle moving along the highway 9, for which a stop signal is at any time being displayed, intersects the beam of light traversing the highway, the photo-sensitive device 325, provided for the highway, is deenergized, and

the exciting coil 35! of a relay 353, associated with the photo-sensitive device 325, is deenergized.

A circuit is closed from one bus line 355, through conductors 351 and 359, a brush 36I associated with an interrupter 363, a segment 365 of the interrupter 363, a bus line 361-connecting the segment 365 of the interrupter to a segment 180 away from it, conductor 369, the movable contactor 313 of the relay 353, associated with the street device that has been actuated, conductor 315, the exciting coil 341 of the relay 343, whereby a ratchet 311 providing for adding resistance to the motor circuit is rotated, conductors 319 and 380, a conducting segment 38!, symmetrically disposed relative to the shaft 383 of the motor 33I, a movable contactor 385, rotated by the motor 33l, a collar 381 secured to the shaft 383 of the motor, a brush 389 in engagement with the collar 381 and conductor 39!, to the di rect-current bus line 393.

It is to be noted that, while the resistance is being added to the motor circuit, the motor windings 333 are not connected to the resistor 335 that is being varied but are connected to the resistor 33'! associated with the'highway II for-which the go signal 6 is being displayed. During the periodof display of the"go signal forthe highway II, the resistor 33'! is'i'ncapable'of variation by'reason of the fact that the coil 349 of the latching relay 345, associated with the resistor, is disconnected from the energizing'circuit, since the movable contactor 395, through which it is energized, is out of engagement with its correspondingfixed segment 391.

The motor is energized from'a circuit extendingfrom one'bus line 355, through the winding 3330f the motor, conductors 399 and 41H, the active section of theresist'or element 331, the mov able contactor 3M, conductors 403 and 389, the segment 38I, the movable contactor 385, the collar 387, the brush 389 and conductor 39I, to the bus line 393.

The interrupter-363 is of such structure that its conducting segments365are long, in=comparison with the insulating elements 495 by which they are separated. Under ordinary circumstances, the interrupter 363 rotates 'at such speed that the conducting segments 365 remain in contact with the brushes 36! during the period that would normallybe occupiedby several interruptions of the'street device. However, ifthe vehicles moving along the highwayfor'whichthe stop signal I "or '2 is being displayed should be arranged in staggered relationship in such manner that the photo-sensitive device 325 or 321, associated with the hi'ghway, isin a deenergize'd condition for a considerable period of time, the interrupter will providethe necessaryinterruptions of the circditjand the resistance will be added to the motor circuit as if'the vehi'c'les h'ad been advancing separated from each other.

Finally, as is illustrated in the drawings, the interrupter 3G3 is directly rotated from the motor-4I5 wherebyit is driven. In many applications"ofthe system, the interrupter will preferably be geared-to the motor in a manner predetermined by thesituation underwhich the system is installed.

The latching systems are provided with pawls 4 I I and M9, whereby the ratchets 311 and HI are held in the positions to which they are rotated against the action of springs" 423 andf' 425 that are secured to the contactors 339 and34l. Whileth e go signal 6 is being displaced for a highway II,'the motor winding 333 is connected in a circuit includingthe resistor 331. Preferably, several seconds before the .go{ signal-6 along'the highwayl Ihanges to a" caution sigrial d, *the relay *429, controlling the 1 position of the holding-'pawhfiw associated with-theratchet an, is energized. Y

The energizing cir'cuit for the relay M9 extends from" a bus line' 355jthrough' conductor 43 I the-exciting coi1 433 of the (relay 42-9associated with f the holding pawl -4 I 9, conductor 43 5 a --'segment lfil disposedadjacentto-the shaft-383 of the pro "am coritrol'motor 33Iya'movable contact'or 439, no'w in engagement with the segment 4373a collar 4 4I,='r'otated by-the motor 33I and a brush "Q43 in en'gagement with the 'collar' l I I ,"to th'ebus line 393. 'Atth-e'same'instant, the movable contactor 395, associated with "the segment 39Tth'at'is connectedtothe coil 349 of the latchmg relay 3 35 of the 'ratchet42 I whereby the "resistance 331 is added to the motor 'circuit,is "r'otated" intoengagement with the'segmeht 3 97, and

the vehicle's advancing along the highway I I are.

now counted by: the latching "relay"3'45.

It willb'e noted that the segments- 431, "whereby the latching relays are deenergized, are comparativelyshort. The reason for the structure is apparent since it is desirable that the vehicles be immediately counted and that as few'vehicles as possible shall go through light beams without being counted.

'I'he pawl 4| 9 is released before the stop signal 2 is displayed along the highway II by reason of the fact that it is desirable that such vehicles as traverse the beam of light, but are obliged to wait for the go signal 6, shall be counted. It is to be noted that, after the contactor 3M reverts to its initial position, the movable contactor 385 remains in engagement with its corresponding segment 38L The motor is, therefore, rotated at an increased speed during the closing seconds of display of the go signal 5 along the highway I i. The period during which this state of affairs exists is comparatively small, and its efiect on the total time of display of the go signal is negligible.

Thecounting of the vehicles along the highway 9-continues until the caution signals 3 and 4 are displayed and, when the signals are displayed, the segment 38] is disengaged from the contactor 385, and the speed of the motor is regulated from the resistor 335, the magnitude of which has been determined by the number of waiting vehicles. The"go signal 5 is, therefore, displayed for a period of time determined by the number of vehicles that were awaiting along the highway i H to'p'ass through the intersection.

'My invention has been shown herein as applied to specific systems, and many details have been shown as incorporated which may not be necessary'in certain systems. However, the essential elements'of my invention are clearly described herein as involving the regulation of the time of display of the go signal for one of a plurality of highways passing through an intersection in accordance with the density of the traffic moving along the highways.

To cover the systems'in which the time of displayofthe signals or the speed of the contacting elements whereby the signals are controlled may be increased aswell as the systems in which these properties may be decreased, I shall use the wordincrement intending that it shall apply in its mathematical sense as having either a positive polarity (in which case it connotes an increase in time orspeed) or a negative polarity (in which case it connotes a decrease in these properties).

Although I have shown and described certain specific embodiments of my invention,-I am fully aware that many modificationsthereof are possible. My invention, therefore,is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In a traflic control system for a plurality of highways of the type incorporating a plurality of stop and go signals to be displayed for said highways, means for energizing said signals, means to be vehicle actuated, said means including photosensitive means and means forv producing a beam of radiant energy to be intersected by vehicles moving along saidhighways to normally energize said photo-sensitive means and means cooperating with said energizing means and said photosensitive means to vary the time of display of said signals; means to respond to the number of interruptions of said'beam of radiant energy by vehicular traflic and coacting with said cooperating means to control the extent to which said cooperative means influences said energizing means thus to control the extent to which the time of display of said signals is varied and means to produce the effect of interruptions of said beam at a predetermined rate on said interruption-responsive means when said beam is continuously interrupted for a predetermined interval of time.

2. A traflic control system for a plurality of highways comprising stop and go signals to be displayed for each of said highways, a plurality of circuits for energizing said signals, a plurality of contactors of predetermined lengths connected in said circuit for closing said circuits for intervals of time proportional to the lengths, means for motivating certain of said contactors relative to certain others of said contactors to successively engage said contactors and to close the corresponding circuits thereby to provide a successive display of stop and go signals for said highways for intervals of time dependent on the lengths of said contactors, said movable contactors having normally a predetermined velocity whereby said stop and go signals are normally displayed for predetermined periods of time, means to be vehicle actuated on each of said highways and means to respond to each actuation of said vehicle-responsive means when it is vehicle actuated to vary the speed of said movable contactors in accordance with the number of actuations of said vehicle responsive means, the

increment in the speed of said movable contactors increasing as the number of actuations of said vehicle-responsive means increases thereby to vary the length of the periods of display of said signals.

3. A traffic control system for a plurality of highways comprising stop and go signals to be displayed for said highways, means for energizing said signals to provide a cyclic display of stop and go signals for one of said highways and go and stop signals for another of said highways, said signals being normally displayed in a predetermined periodic sequence, means to be vehicle actuated in each of said highways and means, responsive to the number of actuations of said vehicle responsive means, when it is actuated by vehicles moving in a highway during the period of time occupied by the display of a go signal for said highway for a predetermined fraction of its period and by the subsequent stop signal for substantially the whole of its period, and cooperating with said energizing means to vary the length of the period of display of the subsequent go signal for said highways in accordance with the number of actuations of said vehicle-responsive means, the increment in the length of the period of display of said go signal increasing as the number of actuations increases.

RICHARD C. HITCHCOCK. 

